It's easy. Just select MP3 as the format to convert to in iTunes's preferences, set the other options as you'd like, then choose Make MP3 Version from the Advanced menu after selecting the songs to convert. (Assuming you're using iTunes 8 - it's slightly different in previous versions of iTunes.)how do u do it on itunes
iTunes is OK, Audacity is better as it uses LAME, Soundtrack Pro is hugely overblown for this kind of task.
I'll second Audacity. You will also need LAME MP3 encoder.
The main problem is i don't want to stay around my computer to do 1 by 1 and check the screen always. And i just know that some apps can convert wav to mp3 in bulk so that it can auto-convert.the onlly problems is that audacity converts 1 by 1. What if you need to convert 50 mp3s?